If a person is entirely without teeth an artificial denture which replaces the missing teeth is said to be "complete", and an artificial denture which replaces the missing teeth of a person possessing some natural teeth is said to be "partial". At the present time, the preferred way of retaining a complete denture is through the suction provided by a peripheral seal of the denture borders with the soft gum tissues, and by the adhesion provided by a saliva film at the interface of the denture and tissue. The preferred way of retaining a partial denture is to employ flexible metal arm-type retainers or clasps which are attached to the denture and engage natural or contrived undercuts which are present on one or more of the remaining natural teeth, or by the use of one or more so-called precision attachments. Such precision attachments consist of two interlocking components, one of which is attached to the denture and the other to a natural tooth.
Partial dentures require skill and care in design, construction and fitting to prevent damage to and possible loss of the remaining natural teeth. The flexible metal arm-type retainers are simpler and less expensive but are less satisfactory in service than the precision attachment retainers. The precision attachment retainers require more complicated clinical and laboratory procedures during denture construction and more care in service and cleaning than the flexible metal arm-type retainers.
Complete dentures are simple to construct but provide little retention, especially in the case of the lower jaw, and the retention available initially may decrease with age because resorbtion of the bony ridges and tissue changes often occur. In addition, the tissues covering the bony ridges are required to absorb the force of chewing, and are thus subject to irritation and trauma. One way of avoiding this trauma is to implant at least one metal, ceramic or plastic material post in the jawbone and to construct the denture using the post(s) for support. This method requires extensive surgical and operative skills.
A variation of this technique involves root filling, decoronating and trimming flush with the gingival margin teeth which would otherwise be extracted, and using the resultant stumps in the same way as implanted posts, either alone or in combination with precision attachments. The first of these procedures provides a so-called overlay denture, and the support provided by the tooth stumps relieves the gums of much of the chewing force, but does not provide retention as such. The second of the two procedures provides a so-called removable precision overlay denture which provides both support and retention, but the tooth stumps used for this purpose are subjected to abnormally high forces during chewing.
The present invention, as hereinafter defined, seeks to avoid the problems associated with self-retained dentures and the use of flexible metal arm or precision attachments by using magnet elements for retaining the dentures in position.